The present invention relates to a storage system capable of encrypting and decrypting data.
As one of the security measures for computer and other systems, there is data encryption technology. (Refer to Japanese Patent Unexamined Publication No. 2002-217887.) A process for performing encryption (hereinafter referred to as “encryption process”) or a process for performing decryption (hereinafter referred to as “decryption process”) are being achieved by the use of semiconductor parts or software. However, when semiconductor parts are used, there is a possibility of occurrence of a malfunction if the parts are subjected to radiation of alpha ray or the like. Whereas, when software is used, there is a risk of such a trouble as a computing error occurring upon arrival of a specific data pattern.
On the other hand, there are increasing demands for enhancement of security of the storage system itself. Generally speaking, when an external device such as a server transmits data to a storage system, it holds the same data as the transmitted data stored in the main memory or the like of the external device until it is confirmed that the data is normally received by the storage system, and deletes the stored data after the confirmation is obtained. Meanwhile, the storage system, upon receipt of the data transmitted from the external device, temporarily stores the data in a cache memory of its own. The storage system, after obtaining confirmation of the data being normally stored in its own disk device, keeps the data stored in the cache memory for a predetermined period of time and deletes the stored data when the predetermined period has passed. (Refer to Japanese Patent Unexamined Publication No. H03-172946).